1. Field of the Invention
The present invention relates to a multilayer substrate including a stack of a plurality of resin base materials formed of thermoplastic resin, and also relates to a manufacturing method for the multilayer substrate.
2. Description of the Related Art
There has been known a multilayer substrate in which a plurality of resin base materials formed of thermoplastic resin are stacked and bonded by heating and pressurization (see, for example, Japanese Unexamined Patent Application Publication No. 2004-311627).
In the above-described multilayer substrate of Japanese Unexamined Patent Application Publication No. 2004-311627, wiring patterns are individually formed on the resin base materials, and the resin base materials are then stacked and bonded to configure a high-frequency circuit.
In the multilayer substrate of Japanese Unexamined Patent Application Publication No. 2004-311627, the resin base materials are disposed all over the multilayer substrate in plan view. That is, the resin base materials of the layers are provided over the entire area of the multilayer substrate in plan view, and the stack number and the position between the layers are constant over the entire area of the multilayer substrate.
Further, there has hitherto been a demand to more densely form wiring patterns in the stacking direction only in one part of a multilayer substrate than in the other part or to change the positions of wiring patterns in the stacking direction only in one part of the multilayer substrate.
However, in the multilayer substrate of the related art described in Japanese Unexamined Patent Application Publication No. 2004-311627, the stack number and the position between the layers cannot be made partially different. In accordance with a part where the stack number is the largest, the stack number and the position between the layers of the resin base materials in the other part are determined inevitably. Hence, the flexibility in design is low. Specifically, for example, when the capacitance of a capacitor is to be increased by decreasing the opposed interval of the wiring patterns in one part and the occurrence of stray capacitance is to be suppressed by increasing the opposed interval of the wiring patterns in the other portion, since the stack number and the position between the layers cannot be made partly different, the stack number and the position between the layers cannot be separately optimized in the parts. Further, in accordance with the part where the largest stack number is required, the stack number of resin base materials in the other part is determined. Hence, the stack number sometimes becomes larger than necessary with respect to the positions of wiring patterns in the other part. At this time, when there is a need to connect wiring patterns provided on different layers (there is a need to connect the layers), the number of connecting portions using via conductors increases more than necessary, and conductivity of connection between the layers is apt to decrease.